Once you have a big audience, the question becomes how do you make it make you money?

The answer is to sell out- or at least sell space on your site. There are multiple options for where to get your ads from, and the preferred plugin to manage it is “ad sense manager” which is a bit of a misnomer since it supports a whole bunch of other sites:

WordPress › AdSense Manager « WordPress Plugins
Version 3.1.x now supports AdSense, AdBrite, AdGridWork, Adpinion, Adroll, Commission Junction, CrispAds, ShoppingAds, Yahoo!PN and WidgetBucks.

Automatic Ad Code Importer for all supported networks. Widgets & Sidebar Modules compatible (as used in the popular K2 theme). Automatic limiting of Ads to meet network T&Cs (Google 3 units/page)

Can’t tell you which ad network to go with- since much of that depends on the kind of audience you attract- but, it’s one way to make a living by blogging.